Implement the new link and hover styles in the prototype kit

[vanitabarrett]

What

We should apply the new link and hover styles to the prototype kit. The new styles will work "out of the box" in general contexts, but we will need to switch on the feature flag. We should make sure the task list and step by step navigation templates are using the new styles.

Why

The new link and hover styles will be opt-in until the next major release of GOV.UK Frontend. However, we'd like the prototype kit to take advantage of the new styles when 3.12.0 is released in order to present the most up-to-date version of GOV.UK Frontend.

Who needs to know about this

Developers

Done when

• We've temporarily installed the new styles through a pre-release of Updates to link styles and link hover states govuk-frontend#2183 in order to preview them
• We've opted into the new link and hover styles (and tested them)
• The task list template is using the new link styles
• The step by step navigation template is using the new link styles

[chao-xian]

+1